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Search Publications by: Howard W. Yoon (Fed)

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Displaying 26 - 50 of 141

Absolute spectral responsivity measurements of solar cells by a hybrid optical technique

July 15, 2013
Author(s)
Behrang H. Hamadani, John F. Roller, Brian P. Dougherty, Fiona Persaud, Howard W. Yoon
An irradiance mode, absolute differential spectral response measurement system for solar cells is presented. The system is based on combining the monochromator-based approach of determining the power mode spectral responsivity of cells with an LED-based

The distance dependences and spatial uniformities of spectral irradiance standard lamps

October 19, 2012
Author(s)
Howard W. Yoon, Gary D. Graham, Robert D. Saunders, Yuqin Zong, Eric L. Shirley
We describe the characterization of a group of NIST spectral irradiance lamps at longer distances and larger angles than are typically issued by NIST. The spectral irradiances from the FEL lamps were measured from 50 cm to 150 cm at 8 different distances

Validation of the dissemination of spectral irradiance values using FEL lamps

September 27, 2012
Author(s)
Bettye C. Johnson, Gary D. Graham, Robert D. Saunders, Howard W. Yoon, Eric L. Shirley
Scales of spectral irradiance are disseminated from NIST by assignment of values to FEL-type lamp standards for defined conditions. These lamp standards can be used for absolute calibration of irradiance radiometers, or more typically, be used in

Comparison of laser-based and monochromator-based thermodynamic temperature measurements

March 19, 2012
Author(s)
George P. Eppeldauer, Howard W. Yoon, Jorge E. Neira, Vladimir Khromchenko, Charles E. Gibson, Allan W. Smith
In this work, we describe the comparisons between the laser-based and monochromator-based radiance responsivity calibrations of a radiation thermometer. The spectral selection of the radiation thermometer is performed using a photopic-response filter which

Extension of the NIST spectral power-responsivity calibration service to 2500 nm

March 2, 2012
Author(s)
George P. Eppeldauer, Howard W. Yoon, Jinan Zeng, Thomas C. Larason, Jeanne M. Houston, Vladimir Khromchenko
The National Institute of Standards and Technology (NIST) is working to extend the upper wavelength limit of the spectral power-responsivity calibration service from 1800 nm to 2500 nm. This extension is based on extended-InGaAs (EIGA) transfer- and

Hyperspectral Image Projector Applications

February 15, 2012
Author(s)
Joseph P. Rice, Steven W. Brown, David W. Allen, Howard W. Yoon, Maritoni A. Litorja, Jeeseong Hwang
For the past several years NIST has been developing, along with several collaborators, a Hyperspectral Image Projector (HIP). This scene projector produces high-resolution programmable spectra and projects them into dynamic two-dimensional images. The

Towards realization of a large-area, LED-based solar simulator

November 27, 2011
Author(s)
Behrang H. Hamadani, Kangbin Chua, John F. Roller, Howard W. Yoon, Brian P. Dougherty
LED-based solar simulators have shown great promise as alternative light sources for indoor testing of PV cells as compared to their traditional counterparts. However, large-area uniform illumination more suitable for larger cells and module measurements

SP250 Spectral Irradiance Calibrations

July 25, 2011
Author(s)
Howard W. Yoon, Charles E. Gibson
This document describes the process of the realization, the maintenance and the dissemination of the spectral irradiance scale and its accompanying uncertainties at the National Institute of Standards and Technology. It describes the measurement procedures

EMPS: Radiation Thermometer Designs

July 1, 2010
Author(s)
Howard W. Yoon, George P. Eppeldauer
Since the publication of the “Theory and Practice of Radiation Thermometry” in 1988, the designs of radiation thermometers have undergone drastic changes. With the exception of few industries, the disappearing filament pyrometers are not commonly used. The

Calibrations of Current-to-Voltage Transimpedance Amplifiers Using Electrical Standards

June 13, 2010
Author(s)
Howard W. Yoon, George P. Eppeldauer, Dean G. Jarrett, Thomas C. Larason, Wan-Seop Kim
For photocurrent measurements with low uncertainties, a wide-dynamic range current-to-voltage converter traceable to resistance standards has been developed at the NIST. The design and calibration of the converter standard are described. For validation

The Extension of the NIST BRDF Scale from 1100 nm to 2500 nm

August 21, 2009
Author(s)
Howard W. Yoon, David W. Allen, George P. Eppeldauer, Benjamin K. Tsai
Measurements of bi-directional reflectance factor for diffuse reflectance from 1100 nm to 2500 nm using extended-range indium gallium arsenide (exInGaAs) detectors in the NIST Spectral Tri-function Automated Reference Reflectometer (STARR) facility are

Spectroradiometric Characterization of the NIST Pulsed Solar Simulator

August 20, 2009
Author(s)
Howard W. Yoon, Brian P. Dougherty, Vladimir Khromchenko
The spectroradiometric characterization of the NIST indoor pulsed solar simulator is described. The solar simulator has a flash duration of 36.4 ms and is designed for solar panels having a maximum size of 2.0 m by 1.6 m. As per industry standards, the

CCPR-S1 Supplementary Comparison for Spectral Radiance in the range of 220 nm to 2500 nm

June 2, 2009
Author(s)
Boris Khlevnoy, Victor Sapritsky, Bernard Rougie, Charles E. Gibson, Howard Yoon, Arnold A. Gaertner, Dieter Taubert, Juergen Hartmann
In 1997, the Consultative Committee for Photometry and Radiometry (CCPR) initiated a supplementary comparison of spectral radiance in the wavelength range from 220 nm to 2500 nm (CCPR S1) using tungsten -strip filament lamps as transfer standards. Five

Non-Contact Temperature Measurements of Micro-Scale Phenomena

October 16, 2008
Author(s)
Howard W. Yoon
Imaging trying to make temprature measurements in a spatial region equal to the edge of a printer paper or within the diameter of a strand of hair. The accurate computer modeling of the machining process requires measurements of the thermodynamic

Spectroradiometric Sources

October 16, 2008
Author(s)
Howard W. Yoon, Charles E. Gibson
rth climate modeling and global impacts of particles and gases in the atmosphere are some of the studies that benefit from the use of spectroradiometers calibrated for spectral irradiance. Spectral irradiance is the optical power incident per unit area of

SSE- and Noise-Optimized InGaAs Radiation Thermometer

October 16, 2008
Author(s)
Howard W. Yoon, Charles E. Gibson, V B. Khromchenko, George P. Eppeldauer
For the measurements of radiance temperatures in the range from 150 ?C to 1000 ?C, low uncertainties in the temperature measurements can be achieved by using near-infrared InGaAs radiation thermometers. We describe the design and construction of the NIST

The Realization and the Dissemination of Thermodynamic Temperature Scales

October 16, 2008
Author(s)
Howard W. Yoon
Since the establishment of the International Temperature Scale of 1190 (ITS-90), much progress has been made in the development of radiometers and blackbody sources. Cryogenic electrical-substitution radiometry is widely used in detector and radiometer